Vibrational spectra of vanadium(V) compounds
VI. Raman spectra of vanadium(V) oxodiperoxo complexes
a
b
P. SCHWENDT and M. PISÁRČIK
a
Department of Inorganic Chemistry, Faculty of Natural Sciences,
Comenius University, CS-842 15 Bratislava
ъ
Institute of Inorganic Chemistry, Centre for Chemical Research,
Slovak Academy of Sciences, CS-842 36 Bratislava
Received 12 February 1987
Dedicated to Professor RNDr. J. Masár, СSc, in honour of his 60 th birthday
Raman spectra of seven vanadium(V) oxodiperoxo complexes have been
measured. On the basis of interpretation of the spectra a reassignment of the
vanadium—ligand stretching vibrations has been proposed. The sensitivity
of the vanadium—peroxo oxygen stretching vibrations to changes in the
coordination polyhedron has been confirmed.
Измерены спектры Рамана семи оксо-дипероксокомплексов вана­
дия^). На основе интерпретации спектров было предложено измене­
ние в отнесении валентных колебаний связей ванадий—лиганд. Полу­
ченные результаты подтвердили чувствительность валентных колеба­
ний связи ванадий—перекисный кислород к изменениям в координа­
ционном полиэдре.
As it follows from interpretation of infrared spectra for a series of peroxo
complexes of vanadium(V) the vanadium—peroxo oxygen stretching modes are
sensitive to changes in the composition and geometry of the coordination sphere
[1]. The spectra enable to distinguish among monoperoxo complexes, pen­
tagonal-pyramidal and pentagonal-bipyramidal diperoxo complexes of vanadium(V).
The aim of this study was to verify the correlation between geometry of
coordination sphere and spectral properties of oxodiperoxo complexes of vanadium(V) by means of interpretation of Raman spectra of the complexes with the
known crystal structure.
Experimental
The complexes were prepared according to published methods: K2[VO(02)2F] [2],
(NH4)2[VO(02)2F] [3], (NH4)3[VO(02)2F2] [4], K3[VO(02)2C03] [5], ^[VOÍO^QOJ •
•H20 [6], (NH4)3[HV203(02)4] [7], (ND4)3[DV203(02)4] [2]. Raman spectra of crystalline
Chem. Papers 42 (3) 305—310(1988)
305
P. SCHWENDT, M. PISÁRČIK
samples were measured on Jeol JRS 1 and Ramalog 3 Spex spectrophotometers using
He-Ne laser. Decomposition was observed even for relatively stable complexes, e.g.
+
K 3 [VO(0 2 ) 2 C0 3 ], when the A r laser was used.
Results and discussion
Oxodiperoxovanadate ions have a low symmetry, therefore all vibrations
corresponding to the site symmetry of the anions are active both in infrared and
Raman spectra. However, Raman spectra are more suitable for investigation of
the v ( V = 0 ) , v(V—Op) (O p — peroxo oxygen), and v(0—O) vibrations, because
the corresponding bands are intensive in comparison with the bands which
correspond to the bending vibrations of ligands. Similarly the V—X stretching
modes (X is a donor atom of the further ligand (Fig. 1)) are observed in Raman
spectra mostly as weak bands*.
Fig. 1. Model of diperoxovanadate ion. Cis and trans positions of peroxo oxygen atoms are related
to the X atom in the pentagonal plane.
When the correlation splitting is not considered, four bands corresponding
to normal vibrations involving predominantly vanadium—peroxo oxygen
stretching vibrations (v l5 v2, v3, and v4(V—Op)) can be expected for the
(0 2 ) V(0 2 ) group. For pentagonal-pyramidal complexes** the Vj and v2(V—Op)
1
vibrations occur at approximately v = 630 cm" (the bands are intensive in the
IR spectrum and weak or medium in the Raman spectrum). The v3 and
v4(V—Op) vibrations occur at about v= 520 cm" 1 (weak or medium bands in
the IR spectrum, one band very strong, the second band medium in the Raman
spectrum) (Table 1). This assignment was confirmed for NH 4 rVO(0 2 ) 2 NH 3 ] by
* It is true especially for the v(V—F) vibrations [8].
** There are only three vanadium(V) diperoxo complexes for which pentagonal-pyramidal
structure has been proved by X-ray analysis: NH 4 [VO(0 2 ) 2 NH 3 ], K2[VO(02)2F], Cs2[VO(02)2F]. The
fourth will be probably N(CH 3 ) 4 [VO(0 2 ) 2 H 2 0], the structure of which is being solved.
306
Chem. Papers 42 (3) 305—310 (1988)
SPECTRA OF VANADIUM(V) COMPOUNDS. VI
Table 1
Raman spectra of diperoxo complexes of vanadium(V) (i>= 200—1000cm"1)
v(NH4[VO(02)2NH3]r
cm
-1
1000 m
957 vs
884 s
623 m
533 vs
503 m
v(K2[VO(02)2F])
cm
-1
*(NH4)2[VCK02)2F])
cm - 1
v(V=0)
950 vs
909 vs
896 s
873 m
881 s
v(0—O)
637 w
626 m
529 vs
489 m
635 sh
619m
511vs
485 w
v,(V-O p )
v 2 (V-O p )
v 3 (V-O p )
v 4 (V-O p )
v(V—N)
446 m
322 s
287 m
Assignment
Bending
vibrations,
v(V-Z)
339 vs
302 m
276 s
352 s
298 w
251m
232 w
v((NH4)3[VO(02)2F2])
*K 3 [VO(0 2 ) 2 C0 3 ])
P(K 3 [VO(0 2 ) 2 C 2 0 4 ].H 2 0)
cm - 1
cm" 1 .
cm"1
961 sh
945 vs
934 vs
924 vs
881s
876 s
859 w
v(0—O)
631m
584 s
485 vs
472 sh
v,(V-O p )
v 2 (V-O p )
v 3 (V-O p )
v 4 (V-O p )
230 w
890 s
865 m
Assignment
v(V=0)
740 vw
693 vw?
638 m
592 m
505 vs
484 sh
630 m
593 s
484 vs
446 vw?
520 s
448 vw
349 s
297 w
268 vw
230 w
Chem. Papers 42 (3)305—310(1988)
v(V—F)
387 m
332 s
296 m
254 vw?
228 vw?
379 m ,
346 s
307 w
257 vw
233 vw
Bending
vibrations,
v(V-Z)
307
P. SCHWENDT, M. PISÁRČIK
Table 1 (Continued)
ví(NH 4 ) 3 [HV 2 0 3 (0 2 ) 4 ])
cm"
1
í/
v((ND 4 ) 3 [DV 2 03(0 2 ) 4 ])
cm"
1
J
Assignment
967 vs
942 s
971 vs
942 s
v(V=0)
881 vs
864 w
884 s
858 sh
v(0—O)
?
608 s
519vs
483 sh
?
607 s
519vs
?
Vi(V-O p )
v 2 (V-O p )
v 3 (V-O p )
v 4 (V-O p )
370 w
324 m
271m
365 w
321m
271m
Bending
vibrations,
v(V-Z)
a) According to [9]; b) bending vibrations of the coordinated carbonato group; c) vibration of
the coordinated oxalato group; d) worse quality spectra.
means of isotopical substitutions N H 3 — N D 3 and 1 4 NH 3 — 1 5 NH 3 , as well as by
normal coordinate analysis [9].
The original assignment for pentagonal-bipyramidal complexes was publish­
ed by Vuletic and Djordjevic [6]. According to their interpretation only two
strong infrared bands at about v = 630 cm" 1 and 590 c m - 1 were assigned to the
v(V—Op) vibrations*. But an analysis of the structural data and a normal
coordinate analysis [10] show that there is no reason why the wavenumber
region of the v(V—Op) vibrations should be more narrow for pentagonal-bipyramidal complexes than for pentagonal-pyramidal complexes. Raman
spectra strongly support this view: intensity ratio for bands assigned to vana­
dium—peroxo oxygen stretching modes is characteristic of and similar for all
diperoxo complexes under study. Analogically to NH4[VO(02)2NH3] a very
strong band at about v = 500 cm" 1 was assigned to v3(V—Op) for all listed
diperoxo complexes (Table 1, Fig. 2). Assignment of the v4(V—Op) vibration is
more problematic and not unambiguous. It seems that corresponding band is
weak in Raman as well as in IR spectra and the coupling of the v4(V—Op) and
v(V—X) vibrations can be expected.
More detailed assignment of bands in the region of bending vibrations of the
0 = V ( 0 2 ) 2 group is not possible. However, it can be supposed that the bands
which are present in the spectra of (NH^fVCKO^F] and (NH 4 ) 3 [VO(0 2 ) 2 FJ
* In our previous papers [1, 2, 5] we accepted this assignment.
308
Chem. Papers 42 (3) 305—310 (1988)
SPECTRA OF VANADIUM(V) COMPOUNDS. VI
and which are missing in the spectrum of K2rVO(02)2F] correspond to normal
modes, which involve stretching vibrations of the long axial V—Z bonds with
the Z atom trans to the double-bonded oxygen. Such a bond is the V---0 bond
(d = 0.2505 nm) which in (NH 4 ) 2 [VO(0 2 ) 2 F] connects two neighbouring units
VO(0 2 ) 2 F into a chain 0 = V - 0 = V . - 0 = V . - [11] or the V—F bond
(d= 0.2306 nm) in (NH^tVOCO^FJ [12]*.
I
1
1
1
1
1
i
i
I
U
b
Ю00
800
600
v/cm"1
400
200
Fig. 2. Raman spectra of (NH 4 ) 2 [VO(0 2 ) 2 F] (a) and (NH^fVCKO^FJ (b).
In a previous paper [1] a criterion for distinguishing between vanadium(V)
diperoxo complexes with the coordination number 6 and 7 by means of the
infrared spectra, was suggested. Although in the mentioned paper the original
assignment of the V—O p stretching vibrations was used, e.g. without v3 and
v4(V—Op), the main conclusions are still valid. These conclusions with respect
to reassignment of some bands can be summarized in the following way: a) The
bands in the region of the V—O p stretching vibrations are the most sensitive to
changes in the coordination sphere, b) When the V—Z bond length is decreas­
ing, the asymmetry of the V(0 2 ) 2 group, e.g. the difference between bond lengths
of two V—O p bonds in one V(0 2 ) group, is increasing. An increase of asym­
metry demonstrates itself in the shift of the band corresponding to v3(V—Op) to
lower wavenumbers, but especially in the increase of separation of the bands
* Other possibility is that these bands correspond to librations of the NH^ ion.
Chem. Papers 42 (3) 305—310 (1988)
309
P. SCHWENDT, M. PISÁRČIK
corresponding to the v,(V—Op) and v2(V—Op) vibrations (Table 2). The
wavenumber difference Av = v,(V—Op) — v2(V—Op) can be thus considered as
a quantity which enables to distinguish between pentagonal-pyramidal
(Av?~ 10cm" 1 ) and pentagonal-bipyramidal (Av~ 40cm" 1 ) complexes.
Table 2
Selected structural and spectral data for diperoxo complexes of vanadium(V)
Complex
CN"
NH 4 [VO(0 2 ) 2 NH 3 ]
Ko[VO(O^F]
(NH 4 ) 3 [HV 2 0 3 (0 2 ) 4 ]
(ND 4 ) 3 [DV 2 0 3 (0 2 ) 4 ]
(NH 4 ) 2 [VO(0 2 ) 2 F]
(NH 4 ) 3 [VO(0 2 ) 2 F 2 ]
K 3 [VO(0 2 ) 2 C0 3 ]
K 3 [VO(0,),C0 4 ]HX>
6
6
6—7
6—7
6—7
7
7
7
</(V-Z)
nm
—
—
0.2520
0.2505
0.2306
0.2301
0.2250
1
i- v
( ' :m
l
0
11
0
0
16
36
37
47
*3
cm '
533
529
519
519
511
505
484
485
Ref.f
[13]
[14]
[15]
[И]
[12]
[16]
[17]
a) CN — the coordination number of vanadium atom. The coordination number 6—7 is given
for pseudopentagonal-bipyramidal coordination [15]. b) From Raman spectra, c) References for
structural data.
References
1. Schwendt, P., Collect. Czechoslov. Chem. Commun. 48, 248 (1983).
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1980.
3. Schwendt, P. and Joniaková, D., Polyhedron 3, 287 (1984).
4. Schwendt, P., Joniaková, D., and Ezr, V., Chem. Papers 39, 353 (1985).
5. Schwendt, P., Petrovic, P., and Úškert, D., Z. Anorg. Allg. Chem. 466, 232 (1980).
6. Vuletic, N. and Djordjevic, C , J, Chem. Soc, Dalton Trans. 1973, 1137.
7. Wieghardt, K. and Quilitzsch, U., Z. Naturforsch. 34B, 242 (1979).
8. Griffith, W. P. and Wickins, T. D., J. Chem. Soc, A 1968, 397.
9. Schwendt, P. and Pisárčik, M., Collect. Czechoslov. Chem. Commun. 47, 1549 (1982).
10. Schwendt, P. and Volka, K., Spectrochim. Acta, in press.
11. Stomberg, R., Acta Chem. Scand. A38, 801 (1984).
12. Stomberg, R., Acta Chem. Scand, A38, 541 (1984).
13. Drew, R. E. and Einstein, F. W. В., Inorg. Chem. 11, 1079 (1972).
14. Stomberg, R., Acta Chem. Scand. A38, 223 (1984).
15. Campbell, N. J., Flanagan, J., Griffith, W. P r , and Skapski, A. C , Transition Met. Chem. 10,
353 (1985).
16. Stomberg, R., Acta Chem. Scand. A39, 725 (1985).
17. Begin, D., Einstein, F. W. В., and Field, J., Inorg. Chem. 14, 1785 (1975).
Translated by P. Schwendt
3 10
Chem. Papers 42 (3) 30S-310(1988)